During dredging operations, weeds or massed vegetation are often encountered that have grown in lagoons, in channels, or in other waters where removal is periodically required. Often the weeds or other aquatic vegetation represents an impediment to the removal of underlying sludge, sand, silt or other deposits.
Many different types of apparatuses have been used for cutting and removing aquatic vegetation. Exemplary devices of the prior art are shown in U.S. Pat. Nos. 669,820; 1,028,671; 1,795,003; 2,223,641; 2,486,275; 2,635,406; 2,702,975; 3,238,708; 3,407,577; 3,468,106; 3,653,192; 4,070,978; 4,095,545; 4,196,566; 4,205,507; 4,416,106; 4,248,033; 4,616,588; and 4,815,260.
A device including an exemplary cutterhead is shown and described in U.S. Pat. No. 5,481,856, which is now commonly owned with the present application. The entire disclosure of U.S. Pat. No. 5,481,856 is hereby incorporated herein by reference. This exemplary cutterhead includes a rotatable drum bearing helical toothed cutting members that cooperate with stationary cutting teeth to tear/cut vegetation. This cutterhead is believed to be particularly effective in resisting wrapping of plant growth around the drum and its ends. However, as best shown in FIGS. 1-3, this prior art cutterhead has been found to damage to the teeth and binding of the drum.
Referring now to FIGS. 1-3, this exemplary prior art cutterhead 10 includes a rotatably mounted drum 12, a shroud 14, drum mounting structure 16 and motor 18. The cutterhead 10 is used in conjunction with a dredge 20 that includes engine compartment 22, pontoon hull 24, deck 25, cab 26, and a boom 28 pivotally mounted at the rear of the dredge. As shown in greater detail in FIG. 2, the boom 28 carries a pump 30 and pump motor 32 for operating the impeller located within the pump 30 and which receives material from the shroud 14 for delivery through the boom 28 to a remote location. The pump motor 32 and the motor 18 are both typically hydraulically driven by hydraulic fluid under pressure by power supplied by a hydraulic pump in the engine compartment 22 and delivered through hydraulic conduits 34 (to pump motor), 36 and 38 (to motor 18).
In greater detail, the drum 12 is substantially cylindrical and presents a smooth outer surface 40 with the exception of an array 42 of spirally oriented, convergent patterned, radially projecting drum teeth 44. The drum 12 may be made of mild steel which provides sufficient strength and durability.
As best shown in FIG. 3, the drum 12 includes a center section 46 and a pair of end sections 48 and 50, each including a pair of end halves. The center section includes an end wall 56 at each longitudinal end and a plurality of circumferentially spaced mounting flanges 56 which project longitudinally at each end and include nuts 60 welded thereto for receiving bolts which project through the surfaces of the end halves 52 and 54 and are threaded into the nuts. This enables easy removal of the end halves 52 and 54 for access to the drum mounting structure 16. As may be seen from FIG. 1, the array 42 extends through the end sections 48 and 50 whereby the spiral orientation of the array 42 is continuous from the ends of the drum 12 across the ends sections 48 and 50 and into the center section 46.
The array 42 includes two convergent helically oriented flights 41 and 43 of mounting plates 62 which are welded to the drum surface 40. The mounting plates 62 are spirally arrayed to provide a toothed cutting surface across virtually the entire width of the drum 12 when teeth 44 are mounted to the plates 62. Each tooth 44 is mounted by two bolts into nuts positioned on the opposite sides of the plates 62, so that every other tooth 44 spans two plates 62. Each tooth 44 presents leading cutting edge 64, a tip 66, and a trailing cutting edge 67, although the motor 18 is preferably a reversible hydraulic motor which permits clearing of the teeth by backwards rotation when necessary. During normal rotation of the teeth, the array 42 converges to an apex 69 to effectively auger the cut and dredged material toward the center of the drum 12.
The shroud 14 includes a pair of opposed end panels 68 and 70 for supporting drum mounting structure 16, upper and lower walls 72 and 74 respectively, angled walls 76 and 78 and back wall 80, all preferably of steel plate. The back wall 80 presents a facing 82 which extends normally above the upper wall 72. A port 84 is centrally located in the back wall and presents a plurality of surrounding holes to facilitate mounting to the pump 30.
Stationary cutterbars 86 and 88 are mounted to the upper and lower walls 72 and 74 respectively. Each cutter bar 86 and 88 presents a plurality of stationary cutterbar teeth 90 which are configured substantially the same as teeth 44 and mount to upstanding flanges 92 on each stationary cutterbar by bolts threaded onto nuts on the other side of the flanges. The spacing of the flanges 92 of each cutterbar 86 and 88, and therefore the teeth 90 carried thereby, is staggered whereby the teeth 90 on cutterbar 86 are not vertically aligned with the corresponding teeth 90 on cutterbar 88. However, the alignment of the teeth 90 corresponds to gaps 94 between the teeth 44 on the drum 12, whereby the slight transverse space between the teeth 44 receives the substantially fore and aft aligned teeth 90 of the stationary cutterbars with the distance between the drum teeth 44 and the cutterbar teeth 90 being about ½″ at the closest point of approach to yield good cleaning and tearing action during rotation. In order to facilitate access to the teeth 90 for maintenance by providing adequate spacing therebetween, not every gap 94 receives a tooth 90 therebetween, but in the preferred embodiment shown, approximately two out of every three gaps 94 will receive a tooth 90 therebetween to provide a tearing relationship between the teeth 90 and the teeth 44 for cutting, writhing and rending any vegetation which wraps around the drum or drapes across the teeth 44 or teeth 90.
The drum mounting structure 16 is largely conventional and includes a hub that permits rotation between the shroud 14 and the drum 12. The hub is bolted to the end panel 70 and to the end wall 56 at one end of the center section of the drum 12. Another hub rigidly connects the motor 18 and the center section 46, and is bolted to the end wall 56 and the motor 18. In turn, the motor 18 is rigidly bolted to the end panel 68 and is preferably a reversible hydraulic motor which enables reversing of the drum 12 to clear any rocks, stumps or other large objects stuck between teeth 44 or teeth 90. The motor 18 is driven by hydraulic fluid supplied under pressure and delivered through conduits 36 and 38. The hubs are located in open-ended cavities and positioned outboard of end walls 56 and radially interior to end sections 48 and 50.
Another exemplary prior art cutterhead is somewhat similar but includes vanes instead of the toothed cutting members shown in FIGS. 1-3. Such vanes extend in helically-convergent flights on the rotatable drum, similar to the toothed cutting members, but are discontinuous along their lengths to define vanes separated by openings that provide clearance for the stationary cutterbar teeth 90 during rotation of the drum. Such vanes are believed to improve upon cutterheads including toothed cutting members in that they provide a double shearing action as vanes pass by on both sides of the stationary teeth.
FIGS. 4 and 5 show an exemplary prior art cutterhead that includes flights of dual-cutting mode vanes. These vanes are of two different types, both of which having leading and trailing edges that extend upwardly from a surface of the drum in a substantially perpendicular direction (substantially radially). A first type of the vanes 120 has a height, as measured from the surface 40 of the drum 12, that is substantially constant along the vane's length (e.g., approximately 3.5 inches above the surface of the drum). These vanes 120 have an outer edge 122 that cooperates with a cutting edge 87 of a shear bar 86 extending longitudinally along the drum, such that during rotation of the drum 12, vegetation is cut between the vane's outer edge 122 and the shear bar 86, thus providing a first mode of cutting action.
A second type of the vanes 130 has a height, as measured from the surface 40 of the drum 12, that varies along the vane's length (e.g., from approximately 3.5 inches above the surface of the drum to approximately 1 inch above the surface of the drum). These vanes 130 are interleaved between the constant height vanes 120, and pairs of the constant- and variable-high vanes cooperate with one another to bound each stationary tooth 90, such that during rotation of the drum 12, vegetation is cut between the stationary tooth 90 and the leading (and trailing) edges of the vanes 120, 130, thus providing a second mode of cutting action.
It is believed that such dual modes of cutting action enhance the cutterhead's cutting performance.
Cattails and plants with long stems and gnarled roots often grow in sediment lagoons and in channels, and when the sediment is to be removed during dredging, these plants are especially tenacious and tend to be difficult to cut. As a result, such vegetation has been known to cause binding (jamming) of the drum and thus the cutterhead. In such a case, the dredging operation is interrupted, and complete removal of the cutterhead and/or the dredging head is often required to remedy the problem, e.g., by replacing the cutterhead.
Therefore, an effective cutterhead is needed that is resistant to such jamming. The present invention fulfills this need among others.